Among proto-rabbis of the first century CE, “building fences around the Torah” was a common practice. The Pharisees (unlike their primary opponents the Sadducees) observed many oral traditions and believed numerous handed down interpretations of Torah. This "oral Torah" was passed down from teacher to student for the generations. These unwritten teachings laid a foundation for the dominant expression of Judaism which emerged after the Jerusalem Temple’s destruction. After 70 CE, without the Temple, Jewish worship was focused on the Holy Scriptures more than ever, and teachings about interpretations of ancient texts became crucial. An essential component of this “oral Torah” was the practice of “building fences around commandments" – formulating additional observances and practices in order to prevent possible disregard of the commandments.
The idea is simple. By observing the “fence rules" one will not be able to come close to accidentally violating the actual commandment. One of the most famous, and most misunderstood, “fences” that Jesus constructed around the Torah is his teaching on anger and murder, found in the Sermon on the Mount in Matt. 5:21-22: “You have heard that the ancients were told, ‘You shall not commit murder’ and ‘Whoever commits murder shall be liable to the court.’ But I say to you that everyone who is angry with his brother shall be guilty before the court; and whoever says to his brother, ‘You good-for-nothing,’ shall be guilty before the supreme court; and whoever says, ‘You fool,’ shall be guilty enough to go into the fiery hell.”
The readers of these verses scratch their heads, thinking “How can anyone never feel anger?” But this is not what Jesus meant. He is telling his disciples that if they entertain anger towards someone, that anger can grow until it becomes verbal abuse. Further unchecked, and allowed to fester one's thoughts and words can lead to violence and even to murder. So if one observes "Yeshua's fence” and is careful to control one's anger, he or she will not end up violating the commandment against murder. Murder usually does not just happen without some conflict and provocation.
Other “fences around the Torah” that Jesus constructs can be seen in the famous Sermon on the Mount:
Vows: Matt. 5:33-37
Justice: Matt. 5:38-42, 38-42
Sexual Morality: Matt. 5:27-30
Mercy: Matt. 5:43-48
All of these passages typically begin with the words “You have heard it said…” followed by a commandment. Then Yeshua says “but I say to you…” and articulates his "fence rules" to safeguard the commencement. Jesus is not changing the original commandment, but instead, he reinforces it by building a “fence” around it and his fence is stricter than the original commandment. The teacher is giving his disciples practical advice will help them to keep the commandment, not to replace it with something new. No wonder that immediately before these teachings begin, Yeshua forcefully asserts that he "did not come to abolish the Law and the Prophets, but to fulfill them" (Matt. 5:17). He tells his listeners that their righteousness must surpass that of the scribes and Pharisees (Matt. 5:20). The “fences around Torah” that he constructs tell his disciples exactly how they can live according to this "greater righteousness".
If Jesus argued with the Pharisees about “building fences around the Torah,” how can it be that Messiah himself also built fences around commandments? Jesus did not object to the building of fences. He objected to the kinds of fences the Pharisees were building, and around what commandments they were building them. They merely argued over priorities. Jesus taught his disciples in a manner similar to the proto-rabbis; a manner entirely common in diverse first-century CE Judaism.